High surface area graphene-supported metal chalcogenide assembly

ABSTRACT

A composition comprising at least one graphene-supported assembly, which comprises a three-dimensional network of graphene sheets crosslinked by covalent carbon bonds, and at least one metal chalcogenide compound disposed on said graphene sheets, wherein the chalcogen of said metal chalcogenide compound is selected from S, Se and Te. Also disclosed are methods for making and using the graphene-supported assembly, including graphene-supported MoS 2 . Monoliths with high surface area and conductivity can be achieved. Lower operating temperatures in some applications can be achieved. Pore size and volume can be tuned. Electrochemical methods can be used to make the materials.

RELATED APPLICATIONS

This Application claims priority to U.S. provisional application61/676,732 filed Jul. 27, 2012, which is incorporated herein byreference in its entirety.

FEDERAL FUNDING STATEMENT

The United States Government has rights in the invention pursuant toContract No. DE-AC52-07NA27344 between the U.S. Department of Energy andLawrence Livermore National Security, LLC, for the operation of LawrenceLivermore National Laboratory.

BACKGROUND

A cost effective and environmentally sound method to convert heavyhydrocarbon feedstocks to liquid fuel would allow the United States todramatically expand the use of biofeedstocks and non-conventionalhydrocarbon resources, including its vast coal reserves. This wouldenhance the economic and energy security of the United States byreducing import of energy from foreign sources. However, current methodsto convert coal and biofeedstocks to liquid require high temperaturesthat in turn lead to significant energy consumption and high CO₂emissions.

To realize the potential of unconventional feedstocks in anenvironmentally sound way, more efficient methods are needed to increasethe hydrogen-to-carbon mole ratio (see FIG. 4). Catalysts based onmolybdenum disulfide that add hydrogen and remove impurities are widelyused in conventional petroleum upgrading, but despite the substantialoverlap in process chemistry, they lack sufficient activity andstability in coals and biofeedstocks conversion processes. More stableand active catalysts are needed both as disposable or recyclableparticles added to slurries during the liquefaction stage and as shapedcatalysts that convert coal and bio-derived liquids to refined productswithin an ebullating or fixed bed reactor. Currently the besthydrotreating catalysts (not utilizing precious metals) are base metal(e.g., Ni, Co, Mo, W) sulfides deposited onto porous alumina supports ofvarious densities and porosities. Base metal sulfide catalysts areunique because they are insensitive to sulfur poisoning and are activein a wide range of temperatures and H₂ pressures.

However, the porous alumina-supported metal sulfide assembly has limitedsurface area (<250 m²/g), is insulating, and generally requires hightemperature for activating the catalyst. Thus, an unmet need exists foran improved porous assembly that has higher surface area, is conductive,has low operating temperature, and enables electrochemical depositionand electrochemical catalysis.

SUMMARY

Embodiments provided herein include compositions, methods and devices.

For example, described here is a composition comprising at least onegraphene-supported assembly, which comprises (i) a three-dimensionalnetwork of graphene sheets crosslinked by covalent carbon bonds and (ii)at least one metal chalcogenide compound disposed on said graphenesheets, wherein the chalcogen of said metal chalcogenide compound isselected from S, Se and Te.

In one embodiment, the metal chalcogenide compound is a catalyst forhydrogenation, hydrodeoxygenation, hydrodesulfurization,hydrodenitrogenation, and/or hydrocracking.

In one embodiment, wherein the graphene-supported assembly iselectrically conductive. In one embodiment, the graphene-supportedassembly has a conductivity of at least 0.5 S/cm.

In one embodiment, the graphene-supported assembly is a monolith havinga size of at least 1 mm³. In one embodiment, the graphene-supportedassembly has an elastic modulus of at least 10 Mpa.

In one embodiment, the chalcogen is S. In one embodiment, the metalchalcogenide compound comprises one or more of Mo, W, Fe, Cd, In, Zn, Niand Co. In one embodiment, the metal chalcogenide compound comprises Moand optionally comprises another metal. In one embodiment, the metalchalcogenide compound comprises MoS₂, WS₂, In₂S₃, CdTe, ZnTe, or anycombination thereof. In one embodiment, the metal chalcogenide compoundcomprises MoS₂.

In one embodiment, the metal chalcogenide compound accounts for at least20 wt % of the graphene-supported assembly.

In one embodiment, the graphene-supported assembly has a surface area ofat least 250 m²/g. In one embodiment, the graphene-supported assemblyhas a mesopore volume of at least 1 cm³/g.

In one embodiment, the metal chalcogenide compound comprises MoS₂,wherein the metal chalcogenide compound accounts for at least 30 wt % ofthe graphene-supported assembly, wherein the graphene-supported assemblyhas a surface area of at least 300 m²/g; and wherein thegraphene-supported assembly is a monolith having a size of at least 1mm³.

In one embodiment, the surfaces of the graphene sheets are substantiallyfree of carbon nanoparticles, and wherein the covalent carbon bondscrosslinking the graphene sheets are primarily sp² bonds.

In one embodiment, the metal chalcogenide compound is Ni—Mo-sulfide orCo—Mo-sulfide. In one embodiment, the composition further comprising(iii) at least one metal oxide, metal carbide or metal nitride depositedon said graphene sheets.

Also described here is a method for making the aforementionedgraphene-supported assembly, comprising: (A) preparing a reactionmixture comprising (i) graphene oxide (GO), (ii) at least one precursorof a metal chalcogenide compound, and (iii) at least one catalyst; (B)curing the reaction mixture to produce a gel; (C) reducing the gel withat least one reducing agent; and (D) drying the gel to produce agraphene-based monolith.

In one embodiment, the reaction mixture comprises at least one organicsolvent and/or water. In one embodiment, the catalyst comprises ammoniumhydroxide. In one embodiment, the reducing agent comprises hydrazine. Inone embodiment, the precursor of the metal chalcogenide compound is(NH₄)₂MoS₄.

In one embodiment, the reaction mixture is cured at a temperature of100° C. or less. In one embodiment, the reaction mixture is cured atambient pressure.

In one embodiment, the step of drying the gel comprises solventexchange. In one embodiment, the step of drying the gel comprisessupercritical drying.

In one embodiment, the method further comprises annealing the dry gel ata temperature of at least 600° C. in an inert atmosphere.

In one embodiment, the metal chalcogenide compound is MoS₂. In oneembodiment, the metal chalcogenide compound is MoS₂, and wherein themethod further comprises incorporating Ni or Co into thegraphene-supported assembly.

In one embodiment, the method comprises simultaneous gelation andreduction of graphene oxide and (NH₄)₂MoS₄ at a temperatures of 100° C.or less.

In one embodiment, the method comprises: dispersing GO in a solution ofDMF and water via bath sonication to produce a suspension, dissolved(NH₄)₂MoS₄ into said suspension, adding ammonium hydroxide to saidsuspension, heating said suspension to produce a gel, adding hydrazineto said gel, heating said gel and said hydrazine to produce aMoS₂-coated gel, washing said MoS₂-coated gel in acetone,supercritically drying said gel with liquid carbon dioxide, andannealing the dry gel.

Also described is another method for making the aforementionedgraphene-supported assembly, comprising: (A) providing a grapheneaerogel, wherein the graphene aerogel comprises a three-dimensionalnetwork of graphene sheets crosslinked by covalent carbon bonds;immersing said graphene aerogel in a solution comprising at least oneprecursor of a metal chalcogenide compound to form a mixture; (B) curingsaid mixture to obtain a wet gel; (C) drying said wet gel to obtain adry gel; and (D) annealing said dry gel to obtain the graphene-supportedassembly.

In one embodiment, the step of curing comprises curing wet gel at atemperature of 100° C. or less, wherein the step of drying comprisessolvent exchange and supercritical drying, and wherein the step ofannealing comprises annealing the dry gel at least 600° C. in an inertatmosphere.

In one embodiment, metal chalcogenide compound is MoS₂, and wherein themethod further comprises incorporating Ni or Co into thegraphene-supported assembly.

Also described is a further method for making the aforementionedgraphene-supported assembly, comprising: (A) providing a grapheneaerogel, wherein the graphene aerogel comprises a three-dimensionalnetwork of graphene sheets crosslinked by covalent carbon bonds; (B)immersing said graphene aerogel in a solution comprising at least oneprecursor of a metal chalcogenide compound; and (C) applying anelectrical current to said graphene aerogel to electrochemically deposita film of said metal chalcogenide compound onto said graphene sheets.

Additionally described is a method for using aforementionedgraphene-supported assembly, comprising contacting said monolith with atleast one hydrocarbon feedstock.

In one embodiment, said hydrocarbon source comprises coal, biofeedstock,and/or petroleum feedstock.

In one embodiment, the metal chalcogenide compound catalyzes thehydrogenation, hydrodeoxygenation, hydrodesulfurization,hydrodenitrogenation, and/or hydrocracking of the hydrocarbon feedstock.

In one embodiment, the metal chalcogenide compound is Ni—Mo-sulfide orCo—Mo-sulfide.

In one embodiment, the method further comprises applying an electricalbias to the monolith to enhance the catalysis.

One advantage of the graphene-supported metal chalcogenide assemblydescribed herein, for at least one embodiment, is high surface area.

Another advantage of the graphene-supported metal chalcogenide assemblydescribed herein, for at least one embodiment, is high conductivity.

Another advantage of the graphene-supported metal chalcogenide assemblydescribed herein, for at least one embodiment, is lower operatingtemperature.

Another advantage of the graphene-supported metal chalcogenide assemblydescribed herein, for at least one embodiment, is the enablement ofelectrochemical deposition and electrocatalysis.

An additional advantage of the graphene-supported metal chalcogenideassembly described herein, for at least one embodiment, is the large andtunable pore volume.

An additional advantage of the graphene-supported metal chalcogenideassembly described herein, for at least one embodiment, is the tunablepore size.

BRIEF SUMMARY OF THE FIGURES

FIG. 1 shows an exemplary graphene-supported MoS₂ monolith after drying.

FIG. 2 shows SEM images of graphene-supported MoS₂ at (a) low and (b)high magnification.

FIG. 3 shows (a) SEM image, EDX maps of (b) sulfur, (c) carbon, (d)molybdenum, and (e) EDX spectrum of graphene-supported MoS₂ monolith.

FIG. 4 shows a diagram of direct liquefaction process. Catalysts areused to increase the hydrogen to carbon ratio. Inexpensive catalysts areused in slurries during the liquefaction process, and high activitycatalysts are used to convert coal liquids to residual. Traditionalrefining spans the upper end of the H:C range.

FIG. 5 shows a schematic visualization of three different elementssuitable for as hydrotreating catalysts: (top) dispersible catalyststhat enhance liquefaction and could be immediately used in coalliquefaction reactors; (middle) multifunctional monolithic catalyststhat could be used in reactor bed technologies; (bottom)electrochemically activated catalysts, which have the potential to tuneselectivity and dramatically increase activity.

FIG. 6 shows a schematic illustration of the applications for thecarbon-chalcogenide assembly described herein.

DETAILED DESCRIPTION Introduction

References cited herein can be used to practice and better understandthe claimed inventions and are incorporated herein by reference in theirentireties for all purposes.

The article, “Mechanically Robust 3D Graphene Macroassembly with HighSurface Area,” Worsley et al., Chem. Commun., 2012, 48, 8428-8430, isincorporated herein by reference in its entirety.

The article, “Synthesis of Graphene Aerogel with High ElectricalConductivity,” Worsley et al., J. Am. Chem. Soc., 2011, 2, 921-925, isincorporated herein by reference in its entirety.

The article, “High Surface Area, sp2-Cross-Linked Three-DimensionalGraphene Monolith,” Worsley et al., J. Phys. Chem. Letter, 2010,132(40), 14067-14069, is incorporated herein by reference in itsentirety.

The article, “Mechanically robust and electrically conductive carbonnanotube foams,” Worsley et al., Appl. Phys. Lett., 2009, 94, 073115, isincorporated herein by reference in its entirety.

The article, “High surface area carbon aerogel monoliths withhierarchical porosity,” Baumann et al., J. Non-Cryst. Solids, 2008, 354,3513, is incorporated herein by reference in its entirety.

The article, “Advanced Carbon Aerogels for Energy Applications,” Bieneret al., Energy & Environmental Science, 2011, 4, 656-667, isincorporated herein by reference in its entirety.

US Patent Publication 2012/0034442 to Worsley et al., “MechanicallyStiff, Electrically Conductive Composites of Polymers and CarbonNanotubes” is incorporated herein by reference in its entirety.

Graphene-Supported Assembly

Many embodiments described herein relate to a composition comprising atleast one graphene-supported assembly, which comprises (i) athree-dimensional network of graphene sheets crosslinked by covalentcarbon bonds and (ii) at least one metal chalcogenide compound disposedon said graphene sheets, wherein the chalcogen of said metalchalcogenide compound is selected from S, Se and Te.

The metal chalcogenide compound can comprises, for example, S. The metalchalcogenide compound can be, for example a metal sulfide. Combinationof metal sulfide can be used.

The metal chalcogenide compound can comprises, for example, one or moremetals. The metal chalcogenide compound can comprises, for example, atleast one of Mo, W, Fe, Cd, In, Zn, Ni and Co. The metal chalcogenidecompound can comprise, for example, at least one of Mo and S. The metalchalcogenide compound can comprise, for example, Mo and another metal,such as Ni or Co.

The metal chalcogenide compound can comprise, for example, at least oneof MoS₂, WS₂, In₂S₃, CdTe and ZnTe, or any combination thereof. Blend ofMoS₂ and WS₂ can be used. The metal chalcogenide compound can comprise,for example, Ni—Mo-sulfide or Co—Mo-sulfide.

The metal chalcogenide compound can be, for example, a catalyst forhydrogenation. The metal chalcogenide compound can be, for example, acatalyst for hydrodeoxygenation. The metal chalcogenide compound can be,for example, a catalyst for hydrodenitrogenation. The metal chalcogenidecompound can be, for example, a catalyst for hydrocracking.

The weight percentage of metal chalcogenide in the graphene-supportedmetal chalcogenide assembly can be, for example, 5-95%, or 10-90%, or20-80%, or 30-60%, or at least 20%, or at least 30%, or at least 50%.

The graphene-supported metal chalcogenide assembly described herein canbe a monolith that is mechanically robust, electrically conductive, andof high-surface area. Monolith is a term known in the art. Monolith andmethods for making monolith are disclosed in, for example, U.S. Pat. No.5,207,814, U.S. Pat. No. 5,885,953, U.S. Pat. No. 5,879,744, U.S. Pat.No. 7,378,188, U.S. Pat. No. 7,410,718, and U.S. Pat. No. 7,811,711. Thegraphene-supported metal chalcogenide assembly can also be a powder orin particle form produced by, for example, grinding or ball-milling themonolith described herein. Methods for conversion to particle or powderform can be adapted to preserve the structures described herein.Particle or powder size can be varied with the methods and instrumentsused.

The graphene-supported metal chalcogenide assembly can be a monolithhaving a size of, for example, or 10³ μm³ or more, or 10⁶ μm³ or more,or 1 mm³ or more, or 1 cm³ or more, or about 10³ μm³ to about 1 mm³, orfrom about 1 mm³ to about 10³ cm³.

The graphene-supported metal chalcogenide assembly can have a thicknessof, for example, 10 μm or more, or 100 μm or more, or 1 mm or more, or 1cm or more, or about 10 μm to about 1 mm, or about 1 mm to about 10 cm.

The graphene-supported metal chalcogenide assembly can have aconductivity of, for example, at least 0.5 S/cm, or at least 1 S/cm, orat least 2 S/cm, or at least 5 S/cm, or about 0.5-10 S/cm.

The graphene-supported metal chalcogenide assembly described herein canhave a surface area of, for example, of 250 m²/g or more, or 300 m²/g ormore, or 350 m²/g or more, or 400 m²/g or more, or 450 m²/g or more, orabout 250-750 m²/g.

The graphene-supported metal chalcogenide assembly described herein canhave a mesopore volume of, for example, of 0.2 cm³/g or more, or 0.5cm³/g or more, or 0.8 cm³/g or more, or 1 cm³/g or more, or 1.2 cm³/g ormore, or about 0.2 to 2 cm³/g.

The graphene-supported metal chalcogenide assembly described herein canhave an compressive modulus of, for example, 10 MPa or more, or 25 MPaor more, or 50 MPa or more, or about 10-50 MPa.

The graphene-supported metal chalcogenide assembly described herein cancomprise a three-dimensional network of graphene sheets crosslinked bycovalent carbon bonds, wherein 50% or more, or 70% or more, or 90% ormore of the crosslinking covalent bonds are sp² bonds.

The graphene-supported metal chalcogenide assembly described herein canbe substantially free of graphene sheets interconnected only by physicalcrosslinks (e.g. Van der Waals forces). For example, thegraphene-supported metal chalcogenide assembly can comprise less than20%, or less than 10%, or less than 5%, or less than 1% of graphenesheets interconnected only by physical crosslinks.

The graphene-supported metal chalcogenide assembly described herein canbe substantially free of graphene sheets interconnected only by metalcrosslinks (e.g., noble metal such as Pd). For example, thegraphene-supported metal chalcogenide assembly can comprise less than20%, or less than 10%, or less than 5%, or less than 1% of the graphenesheets interconnected only by metal crosslinks. The three-dimensionalnetwork of graphene sheets is not made by stacking non-organic material,such as metals, between graphene sheets.

The graphene-supported metal chalcogenide assembly described herein canbe substantial free of graphene sheets with hydroxyl or epoxidefunctionalities. For example, the graphene-supported metal chalcogenideassembly can comprise 5% or less, or 3% or less, or 1% or less, or 0.5%or less, or 0.1% or less of the carbon atoms connected to a hydroxyl orepoxide functionality.

The surfaces of the graphene sheets can be, for example, substantiallyfree of carbon nanoparticles.

The metal chalcogenide can be deposited in the form of nanoparticles inthe graphene-supported assembly described herein. The metal chalcogenidecan be deposited in the form of a film in the graphene-supportedassembly described herein. The metal chalcogenide can be deposited inthe form of a conformal coating in the graphene-supported assemblydescribed herein.

The graphene-supported metal chalcogenide assembly described herein canfurther comprise, for example, at least one metal oxide (e.g., ZrO₂ orzeolites), metal carbide or metal nitride deposited on the graphenesheets. As a result, the graphene-supported metal chalcogenide assemblycan be a multifunctional monolithic catalyst suitable for use in areactor bed of, for example, a coal liquefaction facility. Such metaloxide, metal carbide or metal nitride can be pre-fabricated on thegraphene monolith before the deposition of the metal chalcogenidecompound.

Process for Making Graphene-Supported Metal Chalcogenide Assembly

Many embodiments described herein relate to a method for making theaforementioned graphene-supported metal chalcogenide assembly,comprising: (A) preparing a reaction mixture comprising (i) grapheneoxide (GO), (ii) at least one precursor of a metal chalcogenidecompound, and (iii) at least one catalyst; (B) curing the reactionmixture to produce a gel; (C) reducing the gel with at least onereducing agent; and (D) drying the gel to produce a graphene-basedmonolith.

Methods for making GO are known in the art and disclosed in, forexample, Hummer, J. Am. Chem. Soc., 80:1339 (1958), which isincorporated herein by reference in its entirety.

The reaction mixture can comprise, for example water and/or at least oneorganic solvents, such as alcohol, dimethylformamide, tetrahydrofuran,ethylene glycol, N-methylpyrrolidone, etc. The GO can be dispersed firstin an aqueous suspension by sonicating GO in deionized water. The timefor sonication can range from 0.5-24 hours. The concentration of GO inthe reaction mixture can be 0.1 mg/cc or more, or 1 mg/cc or more, or 2mg/cc or more, or 5 mg/cc or more, or 10 mg/cc or more.

The catalyst in the reaction mixture can be an acid catalyst. Thecatalyst in the reaction mixture can be a base catalyst. Catalystssuitable for making graphene-supported aerogels include, but are notlimited to, nitric acid, acetic acid, ascorbic acid, hydrochloric acid,sulfuric acid, sodium carbonate, sodium hydroxide, ammonium hydroxide,and calcium sulfate. The reactant-to-catalyst ratio may range from 10 togreater than 1000. In a particular embodiment, the catalyst is ammoniumhydroxide.

The precursor of the metal chalcogenide compound can be, for example, amolybdenum salt or a tungsten salt. In a particular embodiment, theprecursor of the metal chalcogenide compound is (NH₄)₂MoS₄. In anotherparticular embodiment, the precursor of the metal chalcogenide compoundis MoO₃. The precursor can also be, for example, a metal oxide or metalthiomettallate applicable for other sulfides (e.g., W, Ni, Co, Fe, etc.)

The reducing agent can be, for example, hydrazine, ammonia, hydrogensulfide, hydrogen/nitrogen, hydrogen/argon, etc. In a particularembodiment, the reducing agent is hydrazine.

The reaction mixture can be cured at a temperature of 100° C. or less toproduce the wet gel. The reaction mixture can be cured at, for example,25-100° C. In a particular embodiment, the reaction mixture is cured at85° C. for 4-168 hours. The reaction mixture can be cured at atmosphericpressure.

The wet gel can be subjected to solvent exchange to remove reactionby-products. Suitable solvent include, but are not limited to, DI water.The wet gel can also be subjected to solvent exchange to remove water.Suitable solvents include, but are not limited to, acetone.

The wet gel can be dried in a supercritical gas to produce a dry gel.Suitable supercritical gases include, but are not limited to,supercritical CO₂. The wet gel can also be dried under ambienttemperature and ambient pressure for an extended time, such as at least24 hours.

The dry gel can be annealed/pyrolyzed in an inert gas at elevatedtemperature. Suitable inert gases include, but are not limited to, N₂.The dry gel can be annealed/pyrolyzed at, for example, 600° C. or more,or 800° C. or more, or 1000° C. or more. The graphene-based assembly canbe carbonized by the annealing/pyrolyzing step.

Wherein a graphene-supported metal chalcogenide assembly is fabricatedaccording to the method described herein, the method can furthercomprise incorporating a promoter metal, such as Ni or Co, into thegraphene-supported assembly. For example, the incorporation of Ni or Cocan produce a graphene-supported Ni—Mo-sulfide assembly or agraphene-supported Co—Mo-sulfide assembly. The method can comprise theimpregnation of a salt of the promoter metal after impregnating themetal halogenide precursor, and the subsequent reduction using thereducing agents described herein. Metal oxides and metal thiometallatescan also be incorporated into the graphene-supported assembly in thisway.

In some embodiments, the method for making the aforementionedgraphene-supported metal chalcogenide assembly comprises (i) thesimultaneous gelation, and (ii) the simultaneous reduction, of grapheneoxide and (NH₄)₂MoS₄ at a temperatures of 100° C. or less.

In some embodiments, the method for making the aforementionedgraphene-supported metal chalcogenide assembly comprises: (a) dispersingGO in a solution of DMF and water via bath sonication to produce asuspension; (b) dissolved (NH₄)₂MoS₄ into said suspension; (c) addingammonium hydroxide to said suspension; (d) heating said suspension toproduce a first gel; (e) adding hydrazine to said first gel; (f) heatingsaid first gel and said hydrazine to produce a second gel; (g) washingsaid second gel in acetone; and (h) supercritically drying said secondgel with liquid carbon dioxide.

Further embodiments for making the aforementioned graphene-supportedmetal chalcogenide assembly comprises: (A) providing a graphene aerogel,wherein the graphene aerogel comprises a three-dimensional network ofgraphene sheets crosslinked by covalent carbon bonds; (B) immersing saidgraphene aerogel in a solution comprising at least one precursor of ametal chalcogenide compound to form a mixture; (C) curing said mixtureto obtain a wet gel; (D) drying said wet gel to obtain a dry gel; and(E) annealing said dry gel to obtain the graphene-supported assembly.

The fabrication of graphene aerogel monoliths are disclosed in US2012/0034442 and Worsley et al., Chem. Commun., 2012, 48, 8428-8430,both of which are incorporated herein by reference in its entirety.

The solution for immersing the graphene aerogel can comprise, forexample, water and/or at least one organic solvent. The precursor of themetal chalcogenide compound can comprise, for example, a molybdenumsalt, a tungsten salt, a iron salt, a nickel salt, a cobalt salt, a zincsalt, a indium salt and/or a cadmium salt. In one particular embodiment,the metal salt comprises a molybdenum salt and/or a tungsten salt. Inanother particular embodiment, the metal salt comprise (NH₄)₂MoS₄.

The concentration of the metal chalcogenide precursor in the mixture canbe, for example, 0.02-10 M, or 0.05-5 M, or 0.1-2M. In addition, themixture can further comprise at least one reducing agent and at leastone catalyst. Suitable catalysts and reducing agents have been describein the foregoing paragraphs.

The curing, drying, and/or annealing conditions have been described inthe foregoing paragraphs.

Additional embodiments for making the aforementioned graphene-supportedmetal chalcogenide assembly comprises: (A) providing a graphene aerogel,wherein the graphene aerogel comprises a three-dimensional network ofgraphene sheets crosslinked by covalent carbon bonds; (B) immersing saidgraphene aerogel in a solution comprising at least one precursor of ametal chalcogenide compound; and (C) applying an electrical current tosaid graphene aerogel to electrochemically deposit a film of said metalchalcogenide compound onto said graphene sheets.

In additional embodiments, electrochemical deposition is an inexpensive,low temperature synthesis route that is enabled by the high electricalconductivity of the graphene scaffolds. Methods for electrodepositingMoS₂ onto conductive substrates are known in the art and disclosed in,for example, Merki et al., Chemical Science 2, 1262 (2011), which isincorporated herein by reference in its entirety.

The reaction mixture can comprise, for example, 2 mM ammonia tetrathiolmolybdate in 0.1 M sodium perchlorate. The pH can remain above ˜5. Thereaction mixture can be buffered between, for example, pH 7 and pH 10using, for example, mixtures of boric acid and sodium borate. Depositioncan occur in the presence or absence of chelating agents such as, forexample, nitrilotriacetic acid (NTA) or ethylenediaminetetraacetic acid(EDTA) that are known to complex metals. Chelators can, for example,shift which metals form a sulfide first and can be used to control theco-deposition of Mo, W, Ni and Co.

In a particular exemplary embodiment, a 2 mM ammonia tetrathiolmolybdate in 0.1 M sodium perchlorate can be adjusted to, for example,pH 9 using 0.1 M boric acid and 0.1 M sodium borate. Deposition cancomprise, for example, ten successive oxidation and reduction cycles atvoltages of −1 V versus Pt wire and +0.2 versus Pt wire. In situ Ramanspectroscopy can be used to confirm that the films reversibly cyclebetween MoS₂ and MoS₃ at −1 V versus Pt wire and +0.2 versus Pt wire,respectively. In a particular embodiment, the voltage can end at, forexample, −1V versus Pt. Conformal coverage can be confirmed with SEM andatomic force microscopy. A final film composition of MoS₂ can beconfirmed using, for example, x-ray photoelectron spectroscopy and Ramanspectroscopy.

In one embodiment, the graphene aerogel subjected to the electrochemicaldeposition of metal chalcogenide is a graphene-supported metal oxidemonolith, which can be produced as described in US 61/745,522,incorporated herein by referenced in its entirety.

Other Carbon-Chalcogenide Assembly

Many embodiments described herein also relate to a compositioncomprising at least one porous carbon aerogel-supported assembly, whichcomprises (i) a porous carbon aerogel, and (ii) at least one metalchalcogenide compound disposed on said graphene sheets, wherein thechalcogen of said metal chalcogenide compound is selected from S, Se andTe.

In one embodiment, the porous carbon aerogel is a mechanically robust,electrically conductive ultralow-density carbon nanotube-based aerogel,which can be produced as described in US 2010/0187484, incorporatedherein by referenced in its entirety.

In one embodiment, the porous carbon aerogel is a high surface area,electrically conductive nanocarbon-supported metal oxide composite,which can be produced as described in US 2012/0122652, incorporatedherein by referenced in its entirety.

In one embodiment, the porous carbon aerogel is a high surface areasilicon carbide-coated carbon aerogel, as well as a metal carbide, metalnitride, or metal carbonitride-coated carbon aerogel, which can beproduced as described in US 2012/0077006, incorporated herein byreferenced in its entirety.

The metal chalcogenide compound can comprises, for example, S. The metalchalcogenide compound can be, for example a metal sulfide. Combinationof metal sulfide can be used.

The metal chalcogenide compound can comprises, for example, one or moremetals. The metal chalcogenide compound can comprises, for example, atleast one of Mo, W, Fe, Cd, In, Zn, Ni and Co. The metal chalcogenidecompound can comprise, for example, at least one of Mo and S. The metalchalcogenide compound can comprise, for example, Mo and another metal,such as Ni or Co.

The metal chalcogenide compound can comprise, for example, at least oneof MoS₂, WS₂, In₂S₃, CdTe and ZnTe, or any combination thereof. Blend ofMoS₂ and WS₂ can be used. The metal chalcogenide compound can comprise,for example, Ni—Mo-sulfide or Co—Mo-sulfide.

The weight percentage of metal chalcogenide in the porous carbonaerogel-supported metal chalcogenide assembly can be, for example,5-95%, or 10-90%, or 20-80%, or 30-60%, or at least 20%, or at least30%, or at least 50%.

The porous carbon aerogel-supported metal chalcogenide assembly can be amonolith having a size of, for example, or 10³ μm³ or more, or 10⁶ μm³or more, or 1 mm³ or more, or 1 cm³ or more, or about 10³ μm³ to about 1mm³, or from about 1 mm³ to about 10³ cm³.

The porous carbon aerogel-supported metal chalcogenide assembly can havea thickness of, for example, 10 μm or more, or 100 μm or more, or 1 mmor more, or 1 cm or more, or about 10 μm to about 10 cm.

The porous carbon aerogel-supported metal chalcogenide assembly can havea conductivity of, for example, at least 0.5 S/cm, or at least 1 S/cm,or at least 5 S/cm, or at least 20 S/cm, or about 0.5-60 S/cm, or about5-40 S/cm.

The porous carbon aerogel-supported metal chalcogenide assemblydescribed herein can have a surface area of, for example, of 300 m²/g ormore, or 500 m²/g or more, or 700 m²/g or more, or about 300-1500 m²/g.

The porous carbon aerogel-supported metal chalcogenide assemblydescribed herein can have an compressive modulus of, for example, 10 MPaor more, or 50 MPa or more, or 100 MPa or more, or about 10-1000 MPa.

Applications

The graphene-supported metal chalcogenide assembly and/or porous carbonaerogel-supported metal chalcogenide assembly described herein can beused in a variety of applications, including, for example, Li storage,hydrogen evolution, decontamination, and fuel upgrading (coal,biofeedstock, etc). See FIG. 6.

In some embodiments, the graphene-supported metal chalcogenide assemblyand/or porous carbon aerogel-supported metal chalcogenide assemblydescribed herein can be used in Li storage. See Li et al., J. Phys.Chem. Lett. 3:2221-2227 (2012); Chang et al., J. Mater. Chem.21:17175-17184 (2011); Chang et al., J. Mater. Chem. 21:6251-6257(2011); and Li et al., Material Letters 63:13663-1365 (2009), all ofwhich are incorporated herein by reference in their entireties.

In some embodiments, the graphene-supported metal chalcogenide assemblyand/or porous carbon aerogel-supported metal chalcogenide assemblydescribed herein can be used in hydrogen evolution. See Kibsgaard etal., Nature Materials 11:963-969 (2012); Benck et al., ACS Catal.2:1916-1923 (2012); Li et al., J. Am. Chem. Soc. 133:7296-7299 (2011);Merki et al., Chemical Science 2, 1262 (2011); Merki et al., Energy &amp; Environmental Science 4, 3878 (2011); and Jaramillo et al., J.Phys. Chem. C 112:17492-17498 (2008), all of which are incorporatedherein by reference in their entireties.

In some embodiments, the graphene-supported metal chalcogenide assemblyand/or porous carbon aerogel-supported metal chalcogenide assemblydescribed herein can be used in decontamination. See Chianelli et al.,Catalysis Reviews 48:1-41 (2006); Abrams et al., Critical Reviews inSolid State and Materials Sciences 30:153-182 (2005); Thurston et al.,J. Phys. Chem. B 103:11-17 (1999); and Wilcoxon et al., Photooxidationof Organic Wastes Using Semiconductor Nanoclusters, U.S. Department ofEnergy Final Report (1997), all of which are incorporated herein byreference in their entireties.

In some embodiments, the graphene-supported metal chalcogenide assemblyand/or porous carbon aerogel-supported metal chalcogenide assemblydescribed herein can be used in fuel upgrading. See Nogueira et al.Applied Catalysis A: General 429-430:92-105 (2012); Lauritsen et al.,Journal of Catalysis 221:510-522 (2004); Lauritsen et al., Journal ofCatalysis 224:94-106 (2004); Farag, Catalysis Today, 1-9 (1999); andSong et al., Energy & amp; Fuels 6, 619-628 (1992), all of which areincorporated herein by reference in their entireties.

Devices Comprising Graphene-Supported Metal Chalcogenide Assembly

Further embodiments relate to a device comprising the graphene-supportedmetal chalcogenide assembly and/or porous carbon aerogel-supported metalchalcogenide assembly described herein. Such device is particularlyuseful in coal liquefaction.

The direct coal liquefaction process (DCL) converts coals to syntheticcrude oil by breaking down large hydrocarbon complexes (100 s ofcarbons) into smaller units (5-20 carbons). In the process, impurityatoms such as sulfur, nitrogen, and oxygen are removed and hydrogen isadded. DCL accomplishes this though the Bergius process in whichhydrogen, heat, and catalysts are used to cleave carbon-carbon bonds(i.e., cracking) and to upgrade products to higher hydrogen to carbonmole ratios (H/C):

These steps are typically broken into two stages: liquefaction andhydrotreating, which have similar goals but often use differentcatalysts and reactor technologies. Additionally, coal liquefactionoffers the option of co-feeding oils based on biofeedstocks that wouldlessen the overall plant carbon footprint.

Catalysts are vital for all aspects of the hydroprocessing train.Hydrogenation and hydrogenolysis catalysts are used to saturatecarbonaceous macromolecules; hydrodesulfurization (HDS),hydrodenitrogenation (HDN), hydrocracking (HYC) catalysts are used toremove sulfur, nitrogen, and oxygen; hydrocracking catalysts (HYC) areused to break carbon-carbon bonds. Exemplary catalysts for localliquefaction are shown in the table below.

Typical Catalyst Primary Action General name NiMo-sulfide Add H withoutHydrogenation breaking Carbon (HYD) bonds NiMo-sulfide HydrogenolysisHydrodeoxygenation Remove oxygen (HDO) CoMo-sulfide HydrogenolysisHydrodesulfurization Remove sulfur (HDS) NiMo-sulfide HydrogenolysisHydrodenitrogenation Remove Nitrogen (HDN) NiW-sulfide, Break C═C bondsHydrocracking ZrO2, Zeolites (HYC)

The device described herein can comprise, for example, one or morecatalysts selected from PE1, PE2, and PE3, which are disclosed in thefollowing paragraphs. A first embodiment, PE1, relates to dispersiblecatalysts for enhancing coal liquefaction (FIG. 5, top). A secondembodiment, PE2, relates to multifunctional monolithic catalystssuitable for use in reactor bed of coal liquefaction reactors (FIG. 5,middle). A third embodiment, PE3, relates to electrochemically activatedcatalysts, which have tunable selectivity and dramatically increaseactivity (FIG. 5, bottom).

PE1 can comprise, for example, a dispersible catalyst comprising thegraphene-supported or porous carbon aerogel-supported metal sulfideassembly described herein. PE1 can comprise, for example, a porouscarbon scaffold with a metal chalcogenide catalyst skin. PE1 cancomprise, for example, a dispersible catalyst comprising agraphene-supported Ni—Mo-sulfide assembly.

The dispersible catalyst can be, for example, in the form of 10-100 μmcolloids. The dispersible catalyst can be, for example, in the form of 1mm spheres. The dispersible catalyst can have peak pore sizes in therange of 20-80 nm. Exemplary PE1 dispersible catalyst are shown in thetable below.

Surface Catalyst C4 + Oil Residue Area Pore Compo- yield Yield Form(m²/g) (nm) sition (wt % d.a.f.) (wt % d.a.f.) 10-100 μm 250-750 20-80NiMoS >75% <5% colloids 1 mm spheres 250-750 20-80 NiMoS >75% <5%

PE2 can comprise, for example, a multifunctional monolithic catalystcomprising the graphene-supported or porous carbon aerogel-supportedmetal sulfide assembly described herein. PE2 can comprise, for example,a porous carbon scaffold with a catalyst skin that contains multiplecatalyst types. PE2 can comprise, for example, a multifunctionalmonolithic catalyst comprising a graphene-supported Ni—Mo-sulfideassembly which further comprises ZrO2 or zeolites. The PE2 can beoptimized for hydrotreating applications within an ebullating bedreactor.

PE2 can be fabricated by, for example, first depositing a partialcoating of metal oxide onto the carbon scaffold as described in US2012/0122652 and US 61/745,522, incorporated by reference in theirentireties, and then depositing the metal sulfide using electrochemicaldeposition as described herein. The metal oxide nanoparticles depositedfirst would mask the underlying substrate so that subsequentelectrochemical deposition of metal sulfide would occur in theconductive carbon regions not masked by the metal oxide.

PE3 can comprise, for example, an electrochemically activated/enhancedcatalyst comprising the graphene-supported or porous carbonaerogel-supported metal sulfide assembly described herein. PE3 cancomprise, for example, a highly conductive carbon scaffold with a metalchalcogenide catalyst skin. PE3 can comprise, for example, anelectrochemically activated/enhanced catalyst comprising agraphene-supported Ni—Mo-sulfide assembly, which optionally comprisesZrO2 or zeolites. The PE3 can be optimized for electrocatalysis oradsorption-induced electrochemical promotion of catalysis (EPOC).

In electrocatalysis, the substrate acts as a reservoir that readilysinks or sources electrons to adsorbed intermediates (through theapplied potential). The intermediates subsequently react with anothersurface or solution species and finally release from the catalyst as aconverted product. This drives redox reactions by providing a surfacefor the intermediate to adsorb to and providing fast electron exchange.By contrast, EPOC occurs when the applied potential polarizes thesurface thereby altering the work function. The change in surface workfunction modifies the adsorbate binding energy, which is directlyrelated to catalysis rates. This follows Sabatier's principle of anoptimal catalyst-adsorbate interaction strength—if binding is too weakadsorbates will not react and if binding is too strong adsorbates willpoison the surface. Sweeping the applied potential, sweeps the workfunction, which sweeps the interaction strength. EPOC is a non-Faradaiceffect thus the solution does not need to sustain a current.

A highly conductive scaffold, such as the graphene-supported or porouscarbon aerogel-supported metal sulfide assembly described herein, isparticularly suitable for use in PE3.

WORKING EXAMPLES Example 1 Co-Synthesis of Graphene-MoS₂ Monolith

In a typical synthesis, 10 mg of graphene oxide (GO) were dispersed in 1ml solution of N,N dimethylformamide (DMF) and water (H₂O) (9:1 ratio ofDMF:H2O) via bath sonication. Next 22 mg of (NH₄)₂MoS₄ were dissolvedinto the suspension. Ammonium hydroxide (133 μl) were then added. Thecontainer was sealed and placed in an oven at 80 C for several hours.After gelation, 100 μl of hydrazine were added and the gel was returnedto the oven for several hours. Finally, the wet gel was removed from theoven, washed in acetone and supercritically dried using liquid carbondioxide. The resulting monolith is black in color and has a density of˜70 mg/cc (FIG. 1).

Scanning electron micrographs of the graphene-supported MoS₂ is shown inFIG. 2. The images show a 3D network of randomly oriented sheet-likestructures similar to those seen in previous reports on reduced GO. Thisresults that the GO gelled as in previous studies and any MoS₂ formedwould be limited to the surfaces of the graphene sheets. Energydispersive x-ray (EDX) analysis confirms the presence of MoS₂ with aMo:S ratio of 0.5 and indicates that it makes up ˜60 wt % of the totalstructure. EDX maps show that the MoS₂ was uniformly distributed overthe graphene surface (FIG. 3). Nitrogen porosimetry measured a surfacearea of 451 m²/g and mesopore volume of 1.16 cm³/g.

Metal chalcogenide, such as metal sulfide, was previously prepared by anumber of techniques, ranging from sol-gel synthesis to chemical vapordeposition to various templating/support methods. For example, theporous MoS₂ materials showed enhanced catalytic activity, compared tobulk material, but most were still limited to surface areas ofapproximately 100 m2/g. This was even the case when using high surfacearea templates such as SBA-15 or MCM-41. Surface areas for the templatedMoS₂ can be less than 200 m2/g. In addition, there were limited workinvolving the use of carbon-based templates/supports which would greatlyenhance the electrical conductivity of the MoS₂ structures used for someelectrochemical and catalytic applications. Lastly, only recently wasthere a report on the fabrication of the MoS₂/graphene composite thatexhibits enhanced hydrogen evolution (Dai et al., J. Am. Chem. Soc.133:7296-7299 (2011)). However, this material appeared to be in the formof powder, required high temperatures (200 C) and pressures (>1 atm) tofabricate, and was not reported to have surface area.

Here, a high surface area 3D graphene-supported MoS₂ monolith was madeby the simultaneous gelation and reduction of graphene oxide and(NH₄)₂MoS₄ at low temperatures/pressures (e.g., 80 C/1 atm). Theresulting dried monoliths had a Mo:S ratio of 0.5 and were ˜60 wt %MoS₂. Surfaces areas of ˜450 m²/g were observed by N₂ porosimetry. Thisroute to high surface area graphene-supported MoS₂ is applicable to awide range of chalcogenides, including WS₂, CdTe, In₂S₃, ZnTe, etc.

Example 2 Chemical Deposition of MoS₂ in Prefabricated Graphene Aerogel

The graphene aerogel was synthesized as described in Worsley et al.,Chem. Commun. 48:8428-8430 (2012), incorporated herein by reference inits entirety. In a typical synthesis, 22 mg of (NH₄)₂MoS₄ were dissolvedin a 1 ml solution of N,N dimethylformamide (DMF) and water (H₂O) (9:1ratio of DMF:H₂O) via bath sonication. Next the graphene aerogel (GA)was immersed in the solution. Ammonium hydroxide (133 μl) and hydrazine(100 μl) were then added. The container was sealed and placed in an ovenat 80 C for several hours. The wet gel was removed from the oven, washedin acetone and supercritically dried using liquid carbon dioxide.Finally samples were annealed at 1050 C in nitrogen for 3 hours.

Example 3 Electrochemical Deposition of MoS₂

Commercially available conductive carbon supports (Highly OrientedPyrolytic Graphite from NT-MDT or Highly Ordered Pyrolytic Graphite fromSPI Supplies) were used for demonstration purposes. In a typicalsynthesis, 2 mM ammonia tetrathiol molybdate in 0.1 M sodium perchloratewas adjusted to pH 9 using 0.1 M boric acid and 0.1 M sodium borate.Deposition consisted of one to ten successive oxidation and reductioncycles at voltages of −1 V versus Pt wire and +0.2 versus Pt wire. Thefinal voltage was stopped at −1V versus Pt. The surface was rinsed inwater and dried in nitrogen gas.

The same process, or substantially the same or similar processes, can beused to electrochemically depositing MoS₂ on the conductive carbonscaffold described herein, including graphene-supported assemblies andporous carbon aerogel-supported assemblies.

What is claimed is:
 1. A composition comprising at least onegraphene-supported assembly, which comprises (i) a three-dimensionalnetwork of graphene sheets crosslinked by covalent carbon bonds and (ii)at least one metal chalcogenide compound disposed on said graphenesheets, wherein the chalcogen of said metal chalcogenide compound isselected from S, Se and Te.
 2. The composition of claim 1, wherein metalchalcogenide compound is a catalyst for hydrogenation,hydrodeoxygenation, hydrodesulfurization, hydrodenitrogenation, and/orhydrocracking.
 3. The composition of claim 1, wherein thegraphene-supported assembly is electrically conductive.
 4. Thecomposition of claim 1, wherein the graphene-supported assembly has aconductivity of at least 0.5 S/cm.
 5. The composition of claim 1,wherein the graphene-supported assembly is a monolith having a size ofat least 1 mm³, or in the form of a powder produced by grinding orball-milling said monolith.
 6. The composition of claim 1, wherein thegraphene-supported assembly has an elastic modulus of at least 10 MPa.7. The composition of claim 1, wherein the chalcogen is S.
 8. Thecomposition of claim 1, wherein the metal chalcogenide compoundcomprises one or more of Mo, W, Fe, Cd, In, Zn, Ni and Co.
 9. Thecomposition of claim 1, wherein the metal chalcogenide compoundcomprises Mo and optionally comprises another metal.
 10. The compositionof claim 1, wherein the metal chalcogenide compound comprises MoS₂, WS₂,In₂S₃, CdTe, ZnTe, or any combination thereof.
 11. The composition ofclaim 1, wherein the metal chalcogenide compound comprises MoS₂.
 12. Thecomposition of claim 1, wherein the metal chalcogenide compound accountsfor at least 20 wt % of the graphene-supported assembly.
 13. Thecomposition of claim 1, wherein the graphene-supported assembly has asurface area of at least 250 m²/g.
 14. The composition of claim 1,wherein the graphene-supported assembly has a mesopore volume of atleast 0.5 cm³/g.
 15. The composition of claim 1, wherein the metalchalcogenide compound comprises MoS₂, wherein the metal chalcogenidecompound accounts for at least 30 wt % of the graphene-supportedassembly, wherein the graphene-supported assembly has a surface area ofat least 300 m²/g; and wherein the graphene-supported assembly is amonolith having a size of at least 1 mm³.
 16. The composition of claim1, wherein the surfaces of the graphene sheets are substantially free ofcarbon nanoparticles, and wherein the covalent carbon bonds crosslinkingthe graphene sheets are primarily sp² bonds.
 17. The composition ofclaim 1, wherein the metal chalcogenide compound is Ni—Mo-sulfide orCo—Mo-sulfide.
 18. The composition of claim 1, further comprising (iii)at least one metal oxide, metal carbide or metal nitride deposited onsaid graphene sheets.
 19. A method for making the composition of claim1, comprising: preparing a reaction mixture comprising (i) grapheneoxide (GO), (ii) at least one precursor of a metal chalcogenidecompound, and (iii) at least one catalyst; curing the reaction mixtureto produce a gel; reducing the gel with at least one reducing agent;drying the gel to produce a graphene-based monolith.
 20. The method ofclaim 19, wherein the reaction mixture comprises at least one organicsolvent and/or water.
 21. The method of claim 19, wherein the catalystcomprises ammonium hydroxide.
 22. The method of claim 19, wherein thereducing agent comprises hydrazine.
 23. The method of claim 19, whereinthe precursor of the metal chalcogenide compound is (NH₄)₂MoS₄.
 24. Themethod of claim 19, wherein the reaction mixture is cured at atemperature of 100° C. or less.
 25. The method of claim 19, wherein thereaction mixture is cured at ambient pressure.
 26. The method of claim19, wherein the step of drying the gel comprises solvent exchange. 27.The method of claim 19, wherein the step of drying the gel comprisessupercritical drying.
 28. The method of claim 19, wherein metalchalcogenide compound is MoS₂.
 29. The method of claim 19, wherein metalchalcogenide compound is MoS₂, and wherein the method further comprisesincorporating Ni or Co into the graphene-supported assembly.
 30. Themethod of claim 19, comprising simultaneous gelation and reduction ofgraphene oxide and (NH₄)₂MoS₄ at a temperatures of 100° C. or less. 31.The method of claim 19, comprising: dispersing GO in a solution of DMFand water via bath sonication to produce a suspension, dissolved(NH₄)₂MoS₄ into said suspension, adding ammonium hydroxide to saidsuspension, heating said suspension to produce a first gel, addinghydrazine to said first gel, heating said first gel and said hydrazineto produce a second gel, washing said second gel in acetone, andsupercritically drying said second gel with liquid carbon dioxide.
 32. Amethod for producing the composition of claim 1, comprising: providing agraphene aerogel, wherein the graphene aerogel comprises athree-dimensional network of graphene sheets crosslinked by covalentcarbon bonds; immersing said graphene aerogel in a solution comprisingat least one precursor of a metal chalcogenide compound to form amixture; curing said mixture to obtain a wet gel; drying said wet gel toobtain a dry gel; and annealing said dry gel to obtain thegraphene-supported assembly.
 33. The method of claim 32, wherein thestep of curing comprises curing wet gel at a temperature of 100° C. orless, wherein the step of drying comprises solvent exchange andsupercritical drying, and wherein the step of annealing comprisesannealing the dry gel at least 600° C. in an inert atmosphere.
 34. Themethod of claim 32, wherein metal chalcogenide compound is MoS₂, andwherein the method further comprises incorporating Ni or Co into thegraphene-supported assembly.
 35. A method for producing the compositionof claim 1, comprising: providing a graphene aerogel, wherein thegraphene aerogel comprises a three-dimensional network of graphenesheets crosslinked by covalent carbon bonds; immersing said grapheneaerogel in a solution comprising at least one precursor of a metalchalcogenide compound; and applying an electrical current to saidgraphene aerogel to electrochemically deposit a film of said metalchalcogenide compound onto said graphene sheets.
 36. A method for usingthe composition of claim 1, comprising contacting said monolith with atleast one hydrocarbon feedstock.
 37. The method of claim 36, whereinsaid hydrocarbon source comprises coal, biofeedstock, and/or petroleumfeedstock.
 38. The method of claim 36, wherein the metal chalcogenidecompound catalyzes the hydrogenation, hydrodeoxygenation,hydrodesulfurization, hydrodenitrogenation, and/or hydrocracking of thehydrocarbon feedstock.
 39. The method of claim 38, wherein the metalchalcogenide compound is Ni—Mo-sulfide or Co—Mo-sulfide.
 40. The methodof claim 38, further comprising applying an electrical bias to themonolith to enhance the catalysis.